Ok here goes. I am renovating a bathroom due to a leaky toilet rotting out the floor. The current subfloor is 1/2" (16" O.C. Joists)there was also a 5/8" underlayment on top of that with vinyl. I want to put ceramic tile down 13X13. My first thought is to add another 1/2" underlayment then (1/4")cement board then tile. This would put the tile about 3/8" higher than the carpet in the hallway. I would then install a transition strip in the doorway. I thought about taking up the entire 1/2" subfloor, but can't figure out how to cut the floor flush at the wall/floor interface. If I go thicker with an underlayment, the transition from tile to carpet could exceed 1/2" is there a limit?